After performing the first direct measurements of the binding enthalpies of the anthracycline drug daunomycin to DNA in the 10 to 20 micromolar range (where the monomeric form predominate), we extended the experiment to study the interaction with other DNA hosts at varying salt concentrations and temperatures. With a differential stopped-flow microcalorimeter, we were able to measure 120 of these enthalpies per day, with an uncertainty of only 3 microjoules. The enthalpy heats ranged from -20 microjoules (endothermic) to +50 microjoules (exothermic).